Method for synergistically composting by using earthworms and lignin degrading bacteria

Abstract

The invention discloses a method for synergistically composting by using earthworms and lignin degrading bacteria. The method comprises the following steps: (1) pretreating raw materials; (2) constructing a biological system to obtain a fermentation culture solution; (3) carrying out earthworm adaptive domestication, firstly carrying out gradient heating training, and then carrying out intestinal flora strengthening training to obtain domesticated earthworms; and (4) layered composting: firstly stacking three fertilizer layers, and then carrying out gradient cooling culture. According to the method, the composting period can be shortened to 25-30 days, the decomposition index (GI value) reaches 85% or above, the humic acid content of the compost product is increased to 12.8 g / kg (the humic acid content in a traditional method is smaller than or equal to 8.5 g / kg), in addition, the cost is effectively reduced, the use amount of exogenous additives is reduced by 40%, and the energy consumption is reduced by 35%.

Description

Technical Field

[0001] This invention relates to the field of composting technology, and in particular to a method for composting using earthworms and lignin-degrading bacteria in synergistic processes. Background Technology

[0002] Current organic waste composting technologies are mainly divided into three categories: Traditional composting relies on natural microbial degradation and requires the addition of conditioning agents such as straw. Typical equipment includes a trough turner and an aeration system. The processing cycle is 45-60 days, and the lignin degradation rate is less than 30%.

[0003] Vermicomposting: This method uses species such as Eisenia fetida to decompose organic matter through digestive enzymes. However, the survival rate of earthworms drops by more than 60% during high-temperature stages (>35℃).

[0004] Microbial agent enhancement method: Inoculation with lignin-degrading bacteria such as white rot fungi requires continuous control of pH (6.5-7.5) and moisture content (55%-65%), which is highly complex.

[0005] In general, the existing technology has the following drawbacks: (1) Bottleneck of lignin degradation: Traditional microorganisms have low efficiency in destroying the structure of lignocellulose, and the residual lignin content in compost products is >18% (by mass).

[0006] (2) Bioactivity conflict: The temperature ranges of earthworms and thermophilic bacteria do not match, resulting in the failure of biosynergy during the high-temperature period (50-65℃) of the pile.

[0007] (3) Severe nutrient loss: Ammonia volatilization loss reaches 25%-40% of total nitrogen (see Transactions of the Chinese Society of Agricultural Engineering, 2021, 37(12)). Summary of the Invention

[0008] The main objective of this invention is to provide a method for composting by synergistic application of earthworms and lignin-degrading bacteria, which can improve composting efficiency.

[0009] To achieve the above objectives, the present invention provides a method for synergistic composting using earthworms and lignin-degrading bacteria, comprising the following steps: (1) Raw material pretreatment The straw is crushed to obtain straw pellets, the pig manure is centrifuged and dehydrated, and then urea is added to obtain conditioned pig manure. (2) Construction of biological systems Pseudomonas chrysospora and Pleurotus ostreatus were inoculated onto activation medium for primary culture. After culture, mycelia were scraped off and mixed to prepare a bacterial suspension with sterile water. The bacterial suspension was inoculated into a seed liquid culture medium for secondary culture. After the culture was completed, the seed liquid was obtained. The seed culture was inoculated into the fermentation medium for three-stage culture. After the culture was completed, the fermentation broth was obtained. (3) Earthworm adaptive domestication Cow dung and lignin are mixed evenly to form a mixed matrix. Earthworms are then mixed into the mixed matrix. Gradual temperature increase training is performed first, followed by gut microbiota enhancement training to obtain domesticated earthworms. (4) Layered composting First, three layers of fertilizer are piled up. The bottom layer is made of sawdust, the middle layer is made of straw pellets and prepared pig manure, and the top layer is made of dry rice straw. Each layer is sprayed with fermentation culture liquid and mixed with domesticated earthworms. After the three layers of fertilizer are piled up, a gradient cooling culture is carried out.

[0010] Furthermore, in step (1), the amount of urea added is such that the C / N ratio of the conditioned pig manure reaches 25-30:1. This ratio is calculated based on the initial carbon and nitrogen content of the straw and pig manure.

[0011] Further, in step (2), the activation medium is PDA medium, and the conditions for primary culture are: static culture in a constant temperature incubator at 28℃ for 72h, culture in the dark for the first 24h, and provide 12h of diffused light per day for the next 48h, with a light intensity of 1000 lux.

[0012] Further, in step (2), the formula of the seed liquid culture medium is: CMC-Na 1.5g / L, (NH4)2SO4 0.3g / L, NHSO4·7H2O 0.05g / L, KH2PO4 0.1g / L, CaCl2 0.02g / L, FeSO4·7H2O 0.001g / L, trace element solution 1mL / L, pH adjusted to 6.8~7.0; the conditions for secondary culture are: 35℃, 180rpm constant temperature shaker culture for 48h.

[0013] Further, in step (2), the fermentation medium formula is as follows: 20 g / L corn flour, 10 g / L soybean meal flour, 1 g / L sodium lignin sulfonate, 0.5 g / L KH2PO4, 0.2 g / L MgSO4·7H2O, 0.01 g / L MnSO4·H2O, 0.001 g / L vitamin B1, and pH adjusted to 6.8-7.2; the conditions for tertiary culture are: temperature 35℃, stirring speed 200 rpm, aeration rate 1.5 vvm, dissolved oxygen maintained at 30-40%, pH adjusted to 6.8-7.2 by adding 1 mol / L HCl or 1 mol / L NaOH, and culture is ended when the lignin peroxidase activity reaches more than 100 U / g.

[0014] Further, in step (3), the moisture content of cow dung is 55%, the lignin content in the mixed substrate is 5%, the earthworms are healthy adult individuals weighing 0.3-0.5g each, and the amount of earthworms mixed in is 100 earthworms mixed in 10kg of mixed substrate; the specific process of gradient temperature training is as follows: the initial temperature is 25℃, the temperature is increased by 2℃ every day, reaching 27℃, 29℃, 31℃, 33℃ and 35℃ in sequence, each temperature gradient is stabilized for 24 hours, and the moisture content of the substrate is maintained at 55-60% during the training period.

[0015] Furthermore, in step (3), the specific process of intestinal flora enhancement training is as follows: the feeding cycle is ≥15 days, 30% of the mixed substrate is replaced daily for the first 5 days, 50% of the mixed substrate is replaced daily for the middle 5 days, and 70% of the mixed substrate is replaced daily for the subsequent period.

[0016] Furthermore, in step (4), the overall cross-section of the three fertilizer layers is trapezoidal, and the earthworm densities of the bottom, middle, and top layers are 350, 400, and 450 earthworms / m², respectively. 3 The bacterial solution spraying rates were 4.5, 5.0, and 5.5 L / m³, respectively. 2 .

[0017] Furthermore, in step (4), the specific process of gradient cooling culture is as follows: first, culture at a high temperature of >50℃ for 3 to 5 days, then culture at a medium temperature of 35 to 50℃ for 10 to 12 days, and finally culture at a low temperature of <35℃ for 7 to 8 days.

[0018] Furthermore, in step (4), aeration control and spray control are carried out during the specific process of gradient cooling culture; Aeration control is as follows: Aeration gas is atmospheric pressure air; when the temperature is >50℃, the blower is started for continuous aeration, with an aeration air volume of 2m³ / h. 3 When the temperature is between 35℃ and 58℃, intermittent aeration is performed, with a cycle of 30s on and 90s off. When the temperature is between 35℃ and 58℃, the blower aeration is stopped and natural ventilation is maintained. Moisture spraying control is as follows: when the moisture content of the pile is <55%, spray clean water until the moisture content recovers to 55-65%; when the pH of the pile is <6.8, spray 0.1mol / L NaHCO3 solution; when the pH is >7.2, spray 0.1mol / L H2SO4 solution.

[0019] The beneficial effects of this invention are reflected in: This invention utilizes the biological characteristics of earthworms, whose coelomic fluid contains unique lignin peroxidase (enzyme activity ≥280U / mg), and designs a stepped temperature control method: a precise temperature control sequence from 55℃ to 35℃ and its corresponding biological activity window (3-5 days for the high-temperature period and 10-12 days for the mesophilic period). By matching a specific aeration frequency (2min / h) with the earthworm's oxygen demand, a cross-temperature zone synergistic mechanism between earthworms and microorganisms is established, achieving dynamic adaptation of the pile temperature. This breaks through the degradation barrier of the lignin-cellulose composite structure, increasing the lignin degradation rate to over 50%. This invention also constructs a nitrogen fixation network, controlling ammonia volatilization loss to within 10%.

[0020] This invention can shorten the composting cycle to 25-30 days, achieve a maturity index (GI value) of over 85%, increase the humic acid content of compost products to 12.8g / kg (compared to ≤8.5g / kg using traditional methods), effectively reduce costs, decrease the use of exogenous additives by 40%, and reduce energy consumption by 35%. Detailed Implementation

[0021] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0022] Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments can be obtained from conventional commercial sources or by existing known methods; unless otherwise specified, the methods used in the embodiments of the present invention are methods mastered by those skilled in the art. Wherein: The selected strains were: Phanerochaete chrysosporium ATCC 24725 and Pleurotus ostreatus FS-J366. These strains could be purchased from commercial sources such as the American Type Culture Collection (ATCC).

[0023] Example 1 Application of earthworms and lignin-degrading bacteria in synergistic composting Includes the following steps: (1) Raw material pretreatment The corn stalks are cut into 5-8cm pieces using a 9FQ-50 chaff cutter, and then crushed into 0.5-1cm pieces using a SWFP-66 hammer mill to obtain stalk pellets. Pig manure with a moisture content of 75% was centrifuged at 3000 rpm to reduce the moisture content to 55%, and then urea was added to make its C / N ratio reach 25:1 to obtain conditioned pig manure. (2) Construction of biological systems 2.1) Primary culture (slant activation): Culture medium formulation: PDA slant medium (potato 200g / L, glucose 20g / L, agar 20g / L) + 0.1% sodium lignosulfonate, pH natural (6.0-6.5). Inoculation amount: On two 15mL PDA slant agar plates, inoculate with a bacterial growth covering half the area of ​​the slant (approximately equivalent to 0.1g of fresh mycelium) of *Plasmodium chrysosporium* and *Pleurotus ostreatus*. Culture conditions: Static culture in a 28℃ constant temperature incubator for 72 hours, with the first 24 hours in the dark, followed by 12 hours of diffused light (1000 lux light intensity) daily for the next 48 hours; Culture process: Regularly observe the mycelial growth status. The mycelial germination rate should reach more than 80% by the 24th hour, the mycelial coverage should reach more than 50% by the 48th hour, and the mycelium should cover the entire slant by the 72nd hour. Avoid contamination during the process. After the culture was completed, 0.2g of *Plasmodium chrysosporium* and 0.2g of *Pleurotus ostreatus* hyphae were scraped off and mixed together to make a bacterial suspension with 5mL of sterile water. 2.2) Secondary culture (shake flask seed culture): Liquid culture medium formula: CMC-Na 1.5g / L, (NH4)2SO4 0.3g / L, NHSO4·7H2O 0.05g / L, KH2PO4 0.1g / L, CaCl2 0.02g / L, FeSO4·7H2O 0.001g / L, trace element solution 1mL / L (ZnSO4·7H2O 0.1g / L, MnSO4·H2O 0.1g / L, CuSO4·5H2O 0.05g / L), pH adjusted to 6.8-7.0; Inoculation amount: 2.5 mL of bacterial suspension per 100 mL of liquid culture medium; Culture conditions: Cultured in a constant temperature shaker at 35℃ and 180rpm for 48 hours; Cultivation process: Samples were taken after 24 hours of cultivation to detect mycelial concentration. When the OD600 value reached 1.2-1.5, cultivation continued. After 48 hours, the lignin peroxidase activity should reach above 50 U / L to obtain the seed culture. 2.3) Three-stage culture (fermenter): Culture medium formula: 20 g / L corn flour, 10 g / L soybean meal flour, 1 g / L sodium lignosulfonate, 0.5 g / L KH2PO4, 0.2 g / L MgSO4·7H2O, 0.01 g / L MnSO4·H2O, 0.001 g / L vitamin B1, pH adjusted to 6.8-7.2; Inoculation amount: 8% volume of secondary shake flask seed liquid (i.e., 4L (50*8%) seed liquid) is added to a 50L fermenter. Culture conditions: temperature 35℃, stirring speed 200rpm, aeration rate 1.5vvm, dissolved oxygen maintained at 30%-40%, pH adjusted to 6.8-7.2 by adding 1mol / L HCl or 1mol / L NaOH; Culture process: The aeration rate is 1 vvm for the first 12 hours of culture, and then adjusted to 1.5 vvm after 12 hours. Samples are taken every 6 hours to detect the bacterial concentration and enzyme activity. The culture is ended when the lignin peroxidase activity reaches 100 U / g or more, and the fermentation culture is obtained for later use.

[0024] (3) Earthworm adaptive domestication The earthworm species used was Eisenia fetida, with healthy adult individuals weighing 0.3-0.5g each. Domestication materials (mixed substrate): 95% cow manure (moisture content 55%) + 5% lignin powder (particle size 0.1-0.2mm). Earthworm density: 100 earthworms per 10 kg of mixed substrate; Gradient temperature increase training: The initial temperature is 25℃, and the temperature is increased by 2℃ each day, reaching 27℃, 29℃, 31℃, 33℃, and 35℃ in sequence. Each temperature gradient is stabilized for 24 hours. During the training period, maintain the substrate moisture content at 55%-60%, ventilate twice a day for 30 minutes each time, observe the activity of earthworms, remove dead individuals in a timely manner, and maintain the survival rate at over 90%. Intestinal flora enhancement training: After the warming training, continue to feed the above mixed substrate for an acclimatization period of ≥15 days. For the first 5 days, replace 30% of the mixed substrate daily, for the middle 5 days, replace 50% of the mixed substrate daily, and for the last 5 days, replace 70% of the mixed substrate daily. During the acclimatization period, record the earthworm feeding rate (which should reach 50%-70% of body weight) and survival rate (≥90%) daily. On the 10th and 15th days, test the lignin-degrading enzyme activity in the earthworm intestinal contents. It should reach more than twice the initial value.

[0025] After gradient temperature increase training and gut microbiota enhancement training, the domesticated earthworms are obtained. (4) Layered composting Composting containers: Rectangular concrete fermentation tanks, each with a volume of 10m (length) × 2.2m (width) × 1.5m (height), and an effective volume of 33m³. 3 .

[0026] Composting equipment: 15rpm trough turner, 2m³ / min blower, temperature sensor, dissolved oxygen detector; dedicated pulse aeration device for fermentation tank (with zoned aeration heads, 0.5m×0.5m spacing between aeration heads, evenly distributed at the bottom of the tank), automatic spraying pipeline system (with adjustable atomizing nozzles, 0.5m spacing between nozzles, spraying radius 0.8m); central control system (linking temperature sensor, dissolved oxygen detector, blower, and spraying system to achieve automatic parameter control).

[0027] Stacking height: 1.2-1.5m, cross-section is trapezoidal (top base width 1.8m, bottom base width 2.2m).

[0028] Three layers of fertilizer were piled up. The bottom layer was made of sawdust, the middle layer was made of a mixture of straw pellets obtained in step (1) and conditioned pig manure (mass ratio 3.5:1), and the top layer was made of dry rice straw. Each layer was sprayed with fermentation culture solution and mixed with domesticated earthworms. After the three layers of fertilizer were piled up, gradient cooling culture was carried out. The earthworm density and the amount of fermentation culture solution added in each layer are shown in Table 1. Table 1

[0029] The specific process of gradient cooling culture is as follows: first, culture at a high temperature (>50℃) for 3–5 days; then, culture at a medium temperature (35–50℃) for 10–12 days; and finally, culture at a low temperature (<35℃) for 7–8 days. The key parameter thresholds for maintaining the temperature gradient are shown in Table 2. Aeration system parameters: Aeration gas: Normal pressure air is used (no need to prepare special gases separately). Aeration method: Aeration is achieved through aeration heads evenly distributed at the bottom of the fermentation tank. Control logic: Temperature > 50℃: Start the blower for continuous aeration, air volume 2m³ / h 3 / min 35℃ < Temperature ≤ 50℃: Perform intermittent aeration (30s on / 90s off cycle). Temperature ≤35℃: Stop mechanical aeration and maintain natural ventilation. Sprinkler system parameters: Spraying feedstock: Regular makeup water: clean water; pH adjustment: spray 0.1 mol / L NaHCO3 solution when the pile pH < 6.8; spray 0.1 mol / L H2SO4 solution when the pH > 7.2; Spraying method: The spray is evenly applied to the surface and interior of the fermentation tank through adjustable atomizing nozzles installed on the top and sides (nozzle spacing 0.5m, spray radius 0.8m). Sprinkler control logic: Moisture content < 55%: Start the sprinkler system to replenish water at a flow rate of 0.5L / min until the moisture content recovers to 55%-65%; Temperature > 58℃: Simultaneously activate the spray system (linked with aeration) to assist in cooling.

[0030] Table 2

[0031] Comparative Example 1 Traditional composting methods (1) Raw material extensive pretreatment Simply crush the straw (corn, wheat straw, etc.) to 8-15cm (no precise particle size control), mix it with livestock manure such as pig manure and cow manure according to the empirical ratio (no strict C / N ratio adjustment, manure accounts for 40%), and naturally adjust the moisture content to 55% (no centrifugal dehydration or urea addition steps).

[0032] (2) Single-unit mass stacking The mixed raw materials are directly piled into rectangular or trapezoidal stacks (1.2m high, 3.0m wide at the bottom, without layered stacking design), and fermentation is started by relying on the natural ambient temperature (without special temperature control equipment, and without a bottom buffer and top covering structure design).

[0033] (3) Manual turning and fermentation Aeration within the pile is maintained solely through regular manual turning (once every 5 days), without any aeration system or bacterial spraying. The degradation process relies entirely on the indigenous microorganisms carried by the raw materials themselves, and no earthworms are added during the fermentation process.

[0034] Experience-based judgment of ripeness After 90 days of composting, maturity is judged by appearance such as "no odor in the compost pile, temperature dropping to ambient temperature, and material turning dark brown". There are no precise testing indicators such as germination index (GI value) and humic acid content. The maturity period is long and the stability is poor.

[0035] Experimental Example 1 Composting effectiveness testing The mixture from step (4) of Example 1, after being layered and composted, was separated into earthworms and compost using a 5mm drum screen. Then, various indicators of the compost were tested, and the results are as follows: Chemical indicators: Water-soluble carbon / organic carbon (WSC / OC) <0.25, ammonium nitrogen / nitrate nitrogen ratio <0.5; Biological detection: Mung bean seed germination index (GI) ≥ 85%; Earthworm avoidance rate (<15%).

[0036] Experiment Example 2 The Influence of Various Factors on Composting Efficiency The compost treated in Example 1 and Comparative Example 1 was tested for relevant indicators, and the results are shown in the following 3: Table 3

[0037] It can be seen that undomesticated earthworms cannot tolerate the composting environment and have low intestinal enzyme activity, resulting in: a decrease in lignin degradation rate (fungus-earthworm synergy fails, relying solely on bacterial solution for degradation); a significant increase in earthworm avoidance rate (undomesticated earthworms have a strong stress response to the composting environment); and an increase in the water-soluble carbon / organic carbon and ammonium-nitrate ratio (incomplete decomposition of organic matter and low nutrient conversion efficiency).

[0038] Reducing the bacterial solution by 50% results in insufficient lignin peroxidase, leading to: a decrease in lignin degradation rate (insufficient enzyme quantity, unable to efficiently decompose lignin); a slight decrease in germination index (reduced bacterial solution leads to incomplete degradation of harmful substances); and a slight increase in earthworm avoidance rate (insufficient bacterial solution worsens the compost microenvironment). The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for synergistic composting using earthworms and lignin-degrading bacteria, characterized in that, Includes the following steps: (1) Raw material pretreatment The straw is crushed to obtain straw pellets, the pig manure is centrifuged and dehydrated, and then urea is added to obtain conditioned pig manure. (2) Construction of biological systems Pseudomonas chrysospora and Pleurotus ostreatus were inoculated onto activation medium for primary culture. After culture, mycelia were scraped off and mixed to prepare a bacterial suspension with sterile water. The bacterial suspension was inoculated into a seed liquid culture medium for secondary culture. After the culture was completed, the seed liquid was obtained. The seed culture was inoculated into the fermentation medium for three-stage culture. After the culture was completed, the fermentation broth was obtained. (3) Earthworm adaptive domestication Cow dung and lignin are mixed evenly to form a mixed matrix. Earthworms are then mixed into the mixed matrix. Gradual temperature increase training is performed first, followed by gut microbiota enhancement training to obtain domesticated earthworms. (4) Layered composting First, three layers of fertilizer are piled up. The bottom layer is made of sawdust, the middle layer is made of straw pellets and prepared pig manure, and the top layer is made of dry rice straw. Each layer is sprayed with fermentation culture liquid and mixed with domesticated earthworms. After the three layers of fertilizer are piled up, a gradient cooling culture is carried out.

2. The method for synergistic composting of earthworms and lignin-degrading bacteria as described in claim 1, characterized in that, In step (1), the amount of urea added is such that the C / N ratio of the conditioned pig manure reaches 25-30:

1.

3. The method for synergistic composting of earthworms and lignin-degrading bacteria as described in claim 1, characterized in that, In step (2), the activation medium is PDA medium, and the conditions for primary culture are: static culture in a constant temperature incubator at 28℃ for 72h, culture in the dark for the first 24h, and provide 12h of diffused light per day for the next 48h, with a light intensity of 1000 lux.

4. The method for synergistic composting of earthworms and lignin-degrading bacteria as described in claim 1, characterized in that, In step (2), the seed liquid culture medium formula is as follows: CMC-Na 1.5g / L, (NH4)2SO4 0.3g / L, NHSO4·7H2O 0.05g / L, KH2PO4 0.1g / L, CaCl2 0.02g / L, FeSO4·7H2O 0.001g / L, trace element solution 1mL / L, pH adjusted to 6.8~7.0; the secondary culture conditions are: 35℃, 180rpm constant temperature shaker culture for 48h.

5. The method for synergistic composting of earthworms and lignin-degrading bacteria as described in claim 1, characterized in that, In step (2), the fermentation medium formula is as follows: 20 g / L corn flour, 10 g / L soybean meal flour, 1 g / L sodium lignin sulfonate, 0.5 g / L KH2PO4, 0.2 g / L MgSO4·7H2O, 0.01 g / L MnSO4·H2O, 0.001 g / L vitamin B1, and pH adjusted to 6.8-7.

2. The conditions for the tertiary culture are: temperature 35℃, stirring speed 200 rpm, aeration rate 1.5 vvm, dissolved oxygen maintained at 30-40%, pH adjusted to 6.8-7.2 by adding 1 mol / L HCl or 1 mol / L NaOH, and culture is ended when the lignin peroxidase activity reaches more than 100 U / g.

6. The method for synergistic composting of earthworms and lignin-degrading bacteria as described in claim 1, characterized in that, In step (3), the moisture content of cow dung is 55%, the lignin content in the mixed substrate is 5%, the earthworms are healthy adult individuals weighing 0.3-0.5g each, and the amount of earthworms mixed in is 100 earthworms mixed in 10kg of mixed substrate; the specific process of gradient temperature training is as follows: the initial temperature is 25℃, the temperature is increased by 2℃ every day, reaching 27℃, 29℃, 31℃, 33℃ and 35℃ in sequence, and each temperature gradient is stabilized for 24 hours. During the training period, the moisture content of the substrate is maintained at 55-60%.

7. The method for synergistic composting of earthworms and lignin-degrading bacteria as described in claim 1, characterized in that, In step (3), the specific process of gut microbiota enhancement training is as follows: the feeding cycle is ≥15 days, 30% of the mixed substrate is replaced daily for the first 5 days, 50% of the mixed substrate is replaced daily for the middle 5 days, and 70% of the mixed substrate is replaced daily for the subsequent period.

8. The method for synergistic composting of earthworms and lignin-degrading bacteria as described in claim 1, characterized in that, In step (4), the overall cross-section of the three fertilizer layers is trapezoidal, and the earthworm densities of the bottom, middle, and top layers are 350, 400, and 450 earthworms / m², respectively. 3 The bacterial solution spraying rates were 4.5, 5.0, and 5.5 L / m³, respectively. 2 .

9. The method for synergistic composting of earthworms and lignin-degrading bacteria as described in claim 1, characterized in that, In step (4), the specific process of gradient cooling culture is as follows: first, culture at a high temperature of >50℃ for 3 to 5 days, then culture at a medium temperature of 35 to 50℃ for 10 to 12 days, and finally culture at a low temperature of <35℃ for 7 to 8 days.

10. The method for synergistic composting of earthworms and lignin-degrading bacteria as described in claim 1, characterized in that, In step (4), aeration and spraying are controlled during the gradient cooling culture process. Aeration control is as follows: Aeration gas is atmospheric pressure air; when the temperature is >50℃, the blower is started for continuous aeration, with an aeration air volume of 2m³ / h. 3 / min, when the temperature is 35℃<50℃, intermittent aeration is performed, with a cycle of 30s on and 90s off. When the temperature is ≤35℃, the blower aeration is stopped and natural ventilation is maintained. Moisture spraying control is as follows: when the moisture content of the pile is <55%, spray clean water until the moisture content recovers to 55-65%; when the pH of the pile is <6.8, spray 0.1mol / L NaHCO3 solution; when the pH is >7.2, spray 0.1mol / L H2SO4 solution.

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